The present invention relates to energy absorbing barrier systems and more particularly to such systems including means for producing signals indicative of system status.
Energy absorbing units for arresting the motion of objects or vehicles have found wide application in the past. For example, U.S. Pat. No. 2,980,213 discloses a system in which a hook trailing from a plane that has landed catches a cable extending across a runway. The ends of the cable are connected to energy absorbers. The energy absorbers each includes a coil of metal which absorbs kinetic energy by being plastically deformed beyond its yield point. Travel of the airplane after landing is significantly limited. Other patents disclosing energy absorbing means include U.S. Pat. No. 2,9791163, 3,017,163, 3,211,260 and 3,366,353. All of the aforementioned patents are commonly assigned with this application. Their disclosures are incorporated by reference herein. Such units have also been used for arresting vertical travel of an elevator whose suspension cable may have broken. More recently, such energy absorbers have been incorporated into roadway systems.
Many fatalities due to collision of a train with a vehicle have been avoided by building of automobile underpasses or train bridges so that a road will not cross railroad tracks. However, cost of widespread implementation of such construction is prohibitive. Such construction has been found to be cost justified in densely populated areas, but may still not be done in areas where a large risk may still exist. It is also desirable to improve safety where possible even at remotely located grade crossings. One way has been to a use barrier comprising a net of Kevlar, (aromatic polyamide fibers) metal or other strong material supported between two columns to arrest vehicle movement. When the barrier is in a deployed state, it defines a restraint zone in which a car will engage the net. The net is coupled to energy absorbers which absorb kinetic energy of the car. The barrier can be moved so that it does not block the restraint zone when it is desired to let traffic pass. The energy absorbers generally comprise metal strips that are plastically deformed to absorb kinetic energy and payout at a rate that provides low deceleration of a vehicle, but sufficient to stop a vehicle in a reasonably distance. Therefore, the energy absorbers are not reusable without servicing and replacement of the metal strip. Replacement is required after an incident in which a crash into a barrier (engagement of a vehicle by the barrier) occurs.
Where many grade crossings are each protected by such a system, it is necessary to monitor the status of each system to know when a crash into a barrier has occurred. In populated areas, occurrence of a crash will be conspicuous. In other areas, visual inspection may be necessary. It is helpful if the organization maintaining the grade crossing protection systems can get prompt notification of a change in the status of any of dozens of unmanned systems within a region served by the maintenance organization.